Ladle skimmer

ABSTRACT

The specification discloses a skimming mechanism used in steel mills for removing slag from the surface of the molten metal in a ladle, the mechanism comprising an extensible boom assembly pivotally mounted on a turntable and power means arranged for rotating the turntable and for pivotally moving the boom assembly in a vertical plane relative to the turntable. The boom assembly comprises telescoping tubular sections, adjustable anti-friction means supporting the inner tubular section within the outer tubular section, a power-actuated driving mechanism comprising cooperating sprocket wheels and roller chains for extending and retracting the inner boom section with respect to the outer boom section, and a skimming paddle comprising a scoop portion separably attached to a mounting bracket portion that is mounted on the outer end of the inner boom section.

United States Patent Barron et a1.

LADLE SKIMMER Inventors: George E. Barron; Harry Pavone,

both of Verona, Pa.

Assignee: Louis A. Grant, Inc., Pittsburgh, Pa.

Filed: Feb. 11, 1974 Appl. No.: 442,006

Related U.S. Application Data [62] Division of Ser. No. 216,997, Jan.11, 1972, Pat. No.

[52] U.S. Cl 214/32; 214/141 [51] Int. Cl. B66c 23/04 [58] Field ofSearch 214/23, 32, 33, 141; 212/55; 52/118, 121; 266/37 [56] ReferencesCited UNITED STATES PATENTS 2,949,201 8/1960 MacAlpine 212/55 2,984,3735/1961 Przyblski 212/55 X 3,659,833 5/1972 Grant 266/37 PrimaryExaminer-Robert G. Sheridan Attorney, Agent, or FirmBuell, Blenko &Ziesenheim [5 7] ABSTRACT The specification discloses a skimmingmechanism used in steel mills for removing slag from the surface of themolten metal in a ladle, the mechanism comprising an extensible boomassembly pivotally mounted on a turntable and power means arranged forrotating the turntable and for pivotally moving the boom assembly in avertical plane relative to the turntable. The boom assembly comprisestelescoping tubular sections, adjustable anti-friction means supportingthe inner tubular section within the outer tubular section, apower-actuated driving mechanism comprising cooperating sprocket wheelsand roller chains for extending and retracting the inner boom sectionwith respect to the outer boom section, and a skimming paddle comprisinga scoop portion separably attached to a mounting bracket portion that ismounted on the outer end of the inner boom section.

2 Claims, 11 Drawing Figures U.S. Patent Oct. 21, 1975 Sheet 1 of53,913,756

lulllldn'lll llllllll l l l l l l l l .l'llllllllll h xll. l alllllrSheet 2 of 5 N ooooodcc i mm om fig m mm US. Patent Oct. 21, 1975 mmHEH.

US. Patent Oct. 21, 1975 Sheet3of5 3,913,756

US. Patent Oct. 21,1975 Sheet 4 of5 3,913,756

| HHI H H IHH H H HUN P l lr l HI I IU MH W I H WWJW W I Sheet 5 of 5US. Patent Oct. 21, 1975 Fig I I.

LAIDLE SKIMMER This is a division of application Ser. No. 216,997, nowUS. Pat. No. 3,800,965, issued Apr. 2, 1974.

The present invention relates to a skimming mechanism for liquids, andmore particularly to a skimming mechanism of the type for removing anoverlying layer of slag or kish from molten metal. Our invention isprimarily intended for, but not necessarily limited to, the removal of amolten slag layer from molten metal in various types of ladles, furnacesand other vessels employed in steel making operations.

In the prior copending application, Ser. No. 107,676, filed Jan. 19,1971, of Louis, A. Grant, now US. Pat. No. 3,659,833, which patent isassigned to the assignee of the present application, there is disclosedand claimed a skimming mechanism for skimming the surface layer of slagor kish from the molten metal in ladles, furnaces and the like. Theaforesaid skimming mechanism comprises an extensible boom, pivotallymounted on a turntable and having on its outer end a pivoted skimmingblade or paddle which is poweractuated to flip the accumulated slag orkish over the lip of the ladle into a receiving vessel.

The extensible boom of the said application comprises outer and innertelescoping tubular boom sections, the inner boom section being guidablysupported within the outer boom section by anti-friction rollers carriedon the bottom and side walls of the outer boom section.

The extension and retraction of the inner boom section relative to theouter boom section is effected by a drive mechanism comprising a rackand pinion arrangement in which a plurality of parallel longitudinallyextending rack members fixed on the upper face of the inner boom sectionare individually engaged by corresponding hydraulic-motor-driven piniongears carried on the outer boom section.

The boom assembly is supported in a desired pivotal position on theturntable, or rocked up and down as desired, by a plurality of hydrauliccylinders on opposite sides of the pivotal connection of the outer boomsection to the turntable.

A double-acting cylinder is located within the inner boom sectionremotely from the skimming blade and has a piston rod which extendsthrough the inner boom section to a pivotal connection with the skimmingblade displaced from the fulcrum thereof for pivotally actuating theblade. Hydraulic pressure connections to the double-acting cylinder areestablished via a pair of flexible hoses carried on a reel mountedadjacent the rear end of the outer boom section. The hoses extendthrough the rear end of the inner boom section and the reelautomatically allows the hoses to lengthen and shorten as necessary tofollow the extension and retraction of the inner boom section.

The skimming mechanism of the aforesaid application has functionedsatisfactorily under service conditions but is open to certaindisadvantages from the standpoint of maintenance and service life. Forexample, the manner in which the inner boom section is guidably mountedwithin the outer boom section on rollers is not flexible enough in viewof the warping of the inner boom section due to exposure to heat. Unlessthe inner boom section remains straight, some binding occurs on theguiding rollers and this increases the friction to the point where theload on the driving motors for the pinions of the rack and pinion drivebecomes excessive. Also the rack and pinion drive employed makes noprovision for dirt elimination. Consequently, the collection of dirt inthe grooves between the teeth on the racks ultimately packs hard andthis prevents proper mating of the pinion gear and rack. In someinstances, stresses have occurred due to the packing of the dirt in therack which have resulted in fracture of the rack, or pinion, or both.Repair of the rack is difficult and time-consuming, with resulting lossof operating time of the skimming mechanism. Also, the method and mannerof connection of the pressure hose from the rear to the double-actingcylinder actuating the pivotal skimming blade, results in wear andabrasion of the hose due to rubbing on the exposed rear edge of theouter boom section when the inner boom section is extended. In addition,the skimming blade collects deposits of slag which harden and interferewith effective skimming performance, as well as pivotal action of theblade. Replacement of the entire blade is thus necessitated which iscostly.

In order to overcome and avoid the aforesaid disadvantages of theskimming mechanism of the aforesaid application, we have devised animproved design of skimming mechanism.

More specifically we have provided a boom assembly of the type havingouter and inner tubular boom sections, the inner boom section beingguidably supported on its bottom surface which rests on flanged rollers,in turn suspended by brackets adjustably attached to the outer boomsection. The rollers extend through holes in the bottom wall of theouter boom section and the inner boom section is centrally guided withinthe outer boom section between the end flanges on the rollers.

We have also provided an improved driving mechanism for extending andretracting the inner boom section, which comprises a plurality oflengths of roller chains the links of which are secured at intervalsalong the length of the chains as by welding certain links to the upperwall of the inner boom section, in longitudinally extending parallelrelation, and a plurality of individually motor-driven sprocket wheelsmounted on the outer boom section and extending through the wall thereofinto engagement with the chains on the inner boom section. Theadjustable guiding rollers supporting the inner boom sectionconcurrently serve to adjust to the appropriate meshing or drivingrelation between the sprocket wheels and the roller chains.

We have also provided an improved arrangement for feeding the pressurehose from the hose reel to the blade-actuating cylinder within the innerboom section. This arrangement comprises mounting the hose reel on arear end extension and feeding the hose through an opening in the sidewall of the inner section to the cylinder. The provision of greaterclearance space between the walls of the outer and inner boom sectionsaccommodates the hose therebetween as the inner boom sectionreciprocates between retracted and extended positions relative to theouter boom section.

We have further provided a new design of skimming paddle comprisingseparable scoop and mounting bracket portions, thus making it possibleto replace the scoop portion without replacement of the mounting bracketportion.

The above features, as well as other features and structural details ofthe presently preferred embodiment of the invention will be elaboratedupon in the forthcoming description, in connection with the accompanyingdrawings, wherein:

FIG. 1 is a general elevational side view of the skimming mechanismcomprising the presently preferred embodiment of the invention, 7

FIG. 2 is a fragmentary elevational side view of the skimming mechanismon enlarged scale, showing front end details of the pivotal blade, thedriving mechanism and the adjustable guide, rollers,

FIG. 3 is a fragmentary elevational side view of the skimming mechanismon the same scale as FIG. 2, showing rear end details,

FIG. 4 is a fragmental plan view of the front end of the skimmingmechanism,

FIGS. 5 and 6 are, respectively, plan and side elevational views of therear end of the skimming mechanism showing mounting details of the hosereel and the hose connections to the inner boom section,

FIGS. 7, 8, 9, and 10 are cross-sectional views, taken on lines VII-VII,VIIIVIII and IX-IX of FIG. 2 and XX of FIG. 3, respectively, and

FIG. 11 is a front end view, looking in the direction of the arrow inFIG. 2, showing-additional details of the skimming paddle and the mannerin which it is mounted.

Referring to FIG. 1 of the drawings, the embodiment of skimmingmechanism shown is generally similar to that shown and described in thecopending application Ser. No. 107,676 of Louis A. Grant, now US. Pat.No. 3,659,833, insofar as the mounting platform, turntable and powercylinders for holding and moving the boom assembly are concerned. Sincereference may be had to the said copending application for a descriptionof these details, they will be identified briefly herein without adetailed description.

As shown in FIG. 1, the skimming mechanism comprises a support structureor platform 10 fabricated of hollow-square girders which may beextensible for accommodating the platform for mounting in a buildingstructure or for otherwise anchoring this platform in position. Ahorizontal mounted on the platform 10 and is rotated by motor 12 througha suitable drive mechanism, such as a chain drive. US. Pat. Nos. 3,47 I,888 and 3,458,396 to Grant et al. and to Grant issued Oct. 14, 1969,and July 29, 1969, show arrangements suitable for mounting and rotatingthe turntable 11.

An extensible boom assembly 13, is pivotally mounted on the turntable 11for pivotal movement in a vertical plane in a manner generally similarto that described for the boom assembly in US. Pat. No. 3,659,833 ofLouis A. Grant. Briefly, a pair of bearing members 14 formed at theupper ends of spaced brackets 14 attached to the turntable serve tosupport opposite ends of a shaft 15 constituting a fulcrum for the boomassembly 13.

As evident from FIG. 1, and particularly shown in FIGS. 7, 8, and 9, theboom assembly 13 comprises two telescoping tubular members,illustratively shown as of square or rectangular cross-section,hereinafter referred to as the outer boom section 16 and the inner boomsection 17. The boom assembly 13 is fulcrummed on the shaft 15 by a pairof spaced bearing brackets 18 attached as by welding to the bottom wallof the outer boom section.

turntable 11 is rotatably' In a manner similar to that described in U.S.Pat. No.

3,659,833 No. of Louis A. Grant a plurality of power cylinders 19 of thedouble-acting type are disposed symmetrically on opposite sides of theshaft 15 for sup porting the boom assembly 13 in a desired position in.

a vertical plane and for effecting pivotal movement thereof to a desiredposition. Itwill be seen that the lower ends of the cylinders 19 arepivotally attached, to the turntable 11 and the distal ends of thepiston rods are pivotally attached by brackets to the wall of the outerboom section 16.

One of the salient improved features of the present invention isprovided by an improved mounting arrangement for the inner boom sectionl7. This arrange-; ment is shown generally in FIG. 1 and comprises aplu-.

rality, illustratively shown as five in number, of flanged rollers 20,disposed in spaced relation along the outer boom section 16 as presentlymore fully described, and extending through openings 21 in thebottomiwall of the outer boom section. As evident in FIGS. 7, 8, and

9, the width of the inner boom section 17 conforms closely to thedistance between the flanges at the ends of the rollers 20, therebybeing guided for reciprocative lers 22 (FIGS. 4 and 9) are mounted inbearing brackets 23 attached to the outer surface of the front end ofouter boom section and extend through a centrally lo-. catedlongitudinal slot 24 (FIG. 4) in the upper wall of the outer boomsection into rolling contact with the upper smooth surface of the innerboom section.

Each roller is rotationally mounted, asbyantifriction bearings atopposite ends, on a shaft 25 which is in turn supported and secured atits opposite endsin I circular holes provided in a pair of brackets 26.Brackets 26 are adjustably attached to the, opposite sidewalls of theouter boom section 16, as shown inFIG. .2. For this purpose thebrackets'have a pair of vertically extending parallel slots 27 (FIG. 2)through which a plurality of screws 28, illustratively shown as three innumber, extend toscrew into corresponding tapped holes in the wall ofthe outer boom section. 7

Certain remotely spaced brackets 26, as shown in FIG. 1, are arrangedfor vertical adjustment by a screw 29 for a purpose presently to beexplained. As seen in FIG. 2, a laterally extending lug 30 is providedonthe wall of the outer boom section for each screw 29. The i lug has ahole through which the screw extends with the head of the screw restingon thetop of the lug.A- nut.

31 is welded to the upper end of the bracket 26, in line forscrew-threaded engagement by the lower end of the screw.

Adjustment of the rollers 20 to provide proper positioning of the innerboom section 17 in the outer boom section 16 is effected by firstadjusting the rollers 20, which can be adjusted by the screws 29, so asto properly align and level the inner boom section within the outer boomsection. Then brackets 26 for the adjusted rollers 20 are locked inposition by tightening screws 28. The remaining rollers 20 aresubsequently adjusted into contact with the bottom surface of the innerboom section and locked in position by tightening screws 28.

This method of adjustment of the position of rollers 20 is particularlyimportant for reasons which will be explained presently in connectionwith the driving mechanism for reciprocating the inner boom section inthe outer boom section.

The driving mechanism for effecting reciprocation of the inner boomsection is a particularly important feature of the invention and willnow be described by particular reference to FIGS. 2, 4, and 8. As shown,a pair of lengths of roller chain 33 are fixed in parallellongitudinally extending relation to the top surface of the inner boomsection 17 for substantially the entire length thereof. Chains 33comprise rollers 34 and connecting links 35. The attachment of the chain33 to the inner boom section is preferably effected by providing anglelinks 35 (FIG. 3) at spaced intervals along the chain 33 to facilitatewelding thereof to the inner boom section. This allows a certainflexible movement to the rollers 34 of the chain which is desirable.

Adjacent the front end of the outer boom section is a transverse slot 36(FIG. 2) to provide access to the chains by a plurality of sprocketwheels 37, each individually driven by a suitable hydraulic motor 38.The mounting arrangement for the sprocket wheels 37 and motors 38comprises two side bracket plates 39 of greater thickness than the wallof the outer boom section inset into the wall slot 36 and welded to thewall. Transverse struts 40 of shallow V-shape are welded at oppositeends to the side plates 39 to provide reinforced support thereto and anenclosure for the sprocket wheels.

Two motors 38 are attached as by screws to each of the opposite sideplates 39 in longitudinal spaced relation, so that they are insubstantial transverse alignment. The sprocket wheels 37 which areremovably attached to the shafts of the motors 38 are positionedtransversely so as to mesh appropriately with a corresponding chain 33.

The functional importance of the adjustable brackets 26 for rollersshould now be apparent in relation to establishing the appropriaterelative positions of the sprocket wheels 37 and the chains 33 forproper transmission of driving forces from sprocket wheels to chains.

It will be understood that the motors 38 at opposite sides of the boomassembly are necessarily actuated concurrently in opposite directions inorder to provide a unidirectional thrust force on the inner boomsection, either for extension or for retraction with respect to theouter boom section. Moreover, by providing a plurality of individuallypower-driven sprocket wheels, there is assurance that operation of theinner boom section may be effected notwithstanding possible failure ofone or more of the motors.

In view of the exposure to very high temperatures radiant from themolten metal in a steel mill environment and also for safety purposes, aso-called heat shield 42 is provided on each side of the outer boomsection in surrounding relation to the motors 38. As will be seen inFIGS. 2, 4, and 8 each of the shields 42 extends longitudinally outsideand underneath the motors 38 and is attached as by angle brackets to thewall of the outer boom section 16.

In order to provide additional support while the inner boom section 17is in extended position, a plurality of supporting rollers 43 aremounted in suitable bearing brackets 44 attached to the rear end of theinner boom section as shown especially in FIGS. 3 and 5. A cam plate 45is attached as by welding to the top wall of the outer boom section atits rear end for engagement by the rollers 43 to insure entrance intothe rear opening of the outer boom section 16.

A skimming blade or paddle 47 is mounted on a U- shaped bracket 48attached as by welding to the outer or forward end of the inner boomsection 17, as particularly shown in FIGS. 1, 2, and 11. The paddle 47is fabricated of sheet steel plates and comprises a separable andreplaceable lower three-sided scoop section 49 and an upper mountingbracket section comprising two spaced mounting plates 50 joined by anintervening angularly disposed generally triangular plate member 51. Thescoop section 49 is closed at the top edge by a transverse plate member52, integrally attached as by welding. To the top surface of the platemember 52, a pair of angle brackets 53 are attached in parallel spacedrelation symmetrically on opposite sides of the longitudinal center line54 (See FIG. 4) of the scoop section, thereby providing longitudinalslots. A pair of spaced gusset plates 55 and 55 are welded to the topplate member 52 and to each of the angle brackets 53 to support them inposition. A pair of gusset plates 56 are also attached to the front faceof the scoop section and to the overhanging end of the angle brackets 53to further support the angle brackets in position.

A bar 57 is attached as by welding to the outside surface of eachmounting plate 50 along the bottom portion thereof. A triangular gussetplate 58 is attached between the inner end of each bar 57 and themounting plate 50 for reinforcement. The scoop section 49 is attached tothe mounting section by sliding the scoop section inwardly so that thebars 57 telescope inside the corresponding groove or slot formed betweeneach angle bracket 53 and the top plate 52 of the scoop section. A wearplate or strip 59 (FIG. 11) is preferably attached to the surface of thetop plate 52 to provide appropriate clearances without lost motionbetween each bar 57 and the corresponding angle bracket.

In order to lock the scoop section to the mounting bracket section, eachbar 57 is provided with a hole 60 therethrough adjacent the front end,and after the scoop section is mounted on the bar, a T-bolt 61 isinserted in the hole. The cross bar of the T-bolt is offset from thecenter line of the bolt, thus providing an exposed portion of the upperend of the bolt. Under operating conditions, the angle brackets 53 shiftback into position covering the exposed portions of the end of theT-bolt as shown in FIG. 4, thus locking the bolt in position againstaccidental removal or dislodgement.

The paddle 47 may be attached to the bracket 48 in a fixed position, ifdesired. However, in the preferred form thereof the paddle is pivotallymounted on the bracket 48. To provide the pivotal mounting, a sleevebearing 62 is attached, as by welding, to the inner edge of thetriangular plate member 51 midway between the mounting plates 50.Attached to the inside of each of the side walls of the U-shaped bracket48 is a sleeve bearing 63, the two bearings 63 being in transversealignment. A pin 64 extending through the bearings 62 and 63 and securedin position by end washers or pins, forms the fulcrum or pivot for thepaddle 47.

Pivotal movement of the paddle 47 is effected by a cylinder 66 of thedouble-acting type (see FIG. 3) located inside the inner boom section 17near the rear end thereof. Cylinder 66 is suitably attached to thebottom wall of the inner boom section. Cylinder 66 has a piston rod 67the distal end of which is hingedly connected by a clevis and pin typeof joint to a long rod 68 which extends longitudinally through the innerboom section to a point adjacent the outer end of the inner boom sectionwhere it is, in turn, hingedly connected by a clevis and pin type ofjoint to a relatively short link rod 69. The rod 68 is supported atintervals through the length of the inner boom section by sleeve typebearing brackets 71, shown in FIGS. 2 and 3, which are dependinglyattached to the upper wall of the inner boom section. Link rod 69 has asleeve bearing 73 at its outer end by means of which a pivotalconnection to the mounting plates is provided. For this purpose a pin 74(FIGS. 2 and 11) is supported at opposite ends in aligned sleeve bosses75 attached to the inside of the mounting plates 50 and extends throughsleeve bearing 73 which is disposed between the bosses 75. Triangulargusset plates 75' provide reinforced support to the bosses 75.

Hydraulic pressure is supplied selectively to the pressure chambers onopposite sides of the double acting piston of cylinder 66, for effectingreciprocative movement of the piston rod 67, through a pair of hoses 77and 78 (FIG. 6). Reciprocative movement of the piston rod 67 effectscorresponding pivotal action of the paddle 47, through the interveningrod 68 and link 69.

Hoses 77 and 78 are wound on a reel 80 carried on two angle brackets 81forming an extension support at the rear end of the outer boom section16. As shown in FIGS. and 6, the hoses enter the interior of the innerboom section 17 through an opening in the side wall thereof, the hosesbeing firmly secured to the outer surface of the side wall by a clamp 82priorto entry into the interior of the inner boom section. Inside theinner boom section hoses 77 and 78 are connected to fittings on thecylinder 66 via which communication is effected to the pressure chamberson opposite sides of the piston in the cylinder.

It'will thus be seen that since opposite ends of the hoses are fixedrelative to the inner boom section 17, noabrasion or wear on the hosesdue to reciprocation of the inner boom section can occur. Of course, theportion of the length of the hoses between the clamp 82 and the reel 80is undertension as the inner boom section is extended, that is, moves tothe left as viewed in FIG. 6. Reel 80 is a conventional type in whichthe hoses are under constant tension and which allows the hoses tounwind to extend in length and automatically re-wind on the reel as theinner boom section 17 is retracted, that is, moves to the right asviewed in FIG. 6.

As is evident in the cross-sectional views, FIGS. 7, 8 and 9, there isadequate clearance space between the side walls of the inner and outerboom sections to accommodate the hoses 77 and 78 therebetween as theinner boom section 17 is extended outwardly. However, a roller 83 (FIG.6) is mounted .in a vertical position on the angle brackets 81 to insurethat the hoses do not rub on the rear end of the outer boom section.Also a double-grooved pulley 84' is mounted on the angle brackets 81 toguide the hoses on the reel 80.

Hydraulic pressure is supplied to the reel 80 from pressure sourcesmounted in the platform through external hose connections 85 and 86.

It will be apparent that if the paddle 47 is attached in a fixedposition to the bracket 48, there is no need for the actuating cylinder66 and the accessory hoses and hose reel and they may, in thatcircumstance, be omit ted.

In order to prevent overtravel of the inner boom section 17 relative toa predetermined ambit in outer. boom section 16, and thereby preventdisengagement of the sprocket wheels 37 from the chains as well asdamage to the skimming paddle 47 and other parts of the mechanism,cushioning limit stops comprising cushioning cylinders 87 and 88 areprovided. As seen in FIGS. 2, 4, and 9, cushioning cylinder 87 ismounted by a suitable bracket on the top wall of the outer boom limit oftravel, the rod 91 engages the piston rod and further travel of theinner boom section 17 is limited by the amount of cushioning travel ofthe piston cylinder 87. When the inner boom section is extended again,bi asing means in the cylinder acts to restore the piston and piston rod90 to the normal position in which it is shown in the drawings.

Cylinder 88 is similar to cylinder 87 and is mounted by a suitablebracket on the side wall of the outer boom section 16 adjacent the frontend thereof. A s.;shown particularly in FIGS. 3 and 8, a lug 94 attachedon the side wall of the inner boom section 17 near the rear end thereofis arranged to engage a Z-bar 95 (FIG. 4) slidably mounted in a slot96in the sidewall of the outer boom section 16, asthe innerboom sectionapproaches the limit of its outward extension. Z-bar 95 is supportedexternally of the slot 96 by a channel member 97 attached in ahorizontal position to the outside surface of the side wall of the outerboom section 16. The outwardly projecting end of Z-bar 95 is biased tothe left,

as seen in FIG. 2, by a coil spring 98 into contact with the end of thechannel member 97.

Piston rod 99 of cushioning cylinder 88 extends longitudinally backtoward and contacts the projecting.

end of the Z-bar 95. Thus, as the inner boom section approaches itslimit of outward extension, lug 94 engages the innerend of the Z-bar 95,which in turn exerts a compressing force on the piston rod 99 ofcushioning cylinder 88. Upon retraction of the inner boom.

section, coil spring 98 restores Z-bar 95 to its normal position and thepiston rod 99 of cylinder 88 is restored concurrently therewith bybiasing means embodied in the cylinder.

For simplicity, the control system by which operation of theturntablemotor 12, the cylinders 19 for pivotally moving and holding the boomassembly, the hydraulic motors 38 for extending and retracting the innerboom section 17, and cylinder 66 for pivoting the paddle 47 iscoordinated is not shown. However, it should be understood that a smallhand-held control device of the push-button type may be employed forconvenient centralized and rapid coordinated remote control of thevarious operations of the skimming mechanism.

In general, the operation of the skimming mechanisrn for removing slagor kish from the top surface ofthe molten metal in a ladle is similar tothat described in the aforementioned US. Pat. No. 3,659,833 of Louis A.Grant. I

It will be understood, therefore, that the ladle containing the moltenmetal is tilted from the vertical until the level of the molten metal issuch as to almostrun out over the lip of the ladle. In such position,the operator extends the inner boom section 17 over the top of the ladleand causes the paddle 47 to assume a position inclined forwardly fromthe vertical so as to parallel the slope of the back wall of the ladle.Thus it is possible for the operator to dip the tip of the paddle 47into the molten metal at the rear of the ladle and by retracting theinner boom section draw an accumulation of slag back toward the lip ofthe ladle. Repeated extension and retraction of the inner boom section,as well as turning of the turntable so as to reach the entire surfacearea of the molten metal in the ladle, enables the operator to quicklyclear the slag from the surface of the metal back over the lip of theladle into a collecting vessel or bucket.

The pivotally mounted paddle 47 is advantageous in several respects.Firstly, if it is desired to employ the paddle in a fixed position, thecylinder 66 may be employed to change the position of the paddle over awide angle from a vertical position to any forwardly inclined positionsuitable to the slope of the back wall of the ladle, which will changeduring the skimming operation with a change in the inclined position ofthe ladle. Secondly, the cylinder 66 may be employed to quickly changethe inclination of the paddle back toward the vertical as't he innerboom section is retracted toward the lip of the ladle to flip or toss anaccumulation of slag over the lip of the ladle into a collecting vessel.

The particular design of paddle and manner of mounting also has certainadvantages over heretofore known constructions. Firstly, becausethescoop section is designed to be separable from the mounting section,replacement only of the scoop section of the paddle will be effectedwhile retaining the mounting section. Because of the accumulation ofmolten slag, which over an extended period of skimming operation,adheres to the scoop section of the paddle, the effective skimmingability of the paddle is impaired. In such cases, it has heretofore beennecessary to replace the entire paddle including the mounting bracketportion thereof. By eliminating the necessity for replacing the mountingbracket portion of the paddle, an appreciable reduction in operatingcost is effected. Moreover, the design of the mounting section of thepaddle guards against the accumulation of slag deposits around the areaof pivotal support of the paddle which would, in the course of time,intefere with the pivotal operation of the paddle. It will be noted thatthe closed bottom of the U-shaped bracket 48 and the skimming platemember 51 between the side members 50 prevents the deposit andaccumulation of slag around the fulcrum pin 64 and sleeve bearings 62and 63, thus increasing the service life of the mounting bracket sectionand making it possible to retain the mounting section when the scoopsection of the paddle is replaced.

A particular advantage of the invention resides in the sprocketwheel-roller chain type of drive for extension and retraction of theinner boom section. This type of drive is self-cleaning, therebyeliminating the accumulation of dirt in the parts, in contrast to theprevious rack and pinion type of drive. Moreover, repair or replacementof individual links or rollers of the chain reduces the maintenanceexpense as well as the time required to effect repair in the event ofthe breakage of parts compared to the rack and pinion type of drive.

Furthermore, the manner and means for adjustably mounting the rollers 20is advantageous in that it concurrently makes possible the relativeadjustment of sprocket wheel 37 and the roller chains for appropriatedriving effectiveness without additional means for this purpose.

It should be observed also that the manner of mounting the hose reel andthe connection of the hoses 77 and 78 to the paddle-operating cylinder66 eliminates difficulties and breakdown due to wear and breakage ofhoses in prior designs of skimming mechanism.

In summary, it will be seen that the skimming mechanism which we haveprovided has numerous advantages over prior designs, all of whichcontribute to a more effective skimming operation, as well as to longerintervals between shutdowns for overhaul or maintenance operations ofthe apparatus. Moreover, the cost of operation and maintenance isreduced over prior designs of skimming mechanism.

While the presently preferred embodiment of the invention has beendescribed and disclosed herein, it will be apparent that variations inthe embodiment and in the manner of its use are possible, within theterms of the appended claims.

We claim:

1. In a skimming mechanism having a supporting structure, a boomassembly movably mounted on said structure, said boom assembly havingtelescoping outer and inner boom sections, anti-friction means guidablysupporting said inner boom section for reciprocative movement withinsaid outer boom section, a skimming paddle carried on the forward end ofsaid inner boom section, and power drive means for effectingreciprocative movement of said inner boom section within said outer boomsection, the improvement comprising a pair of cushioning cylinders fixedexternally at the front end of said outer boom section, one of saidcylinders having a forwardly projecting piston rod and the other of saidcylinders having a rearwardly projecting piston rod, rod means on saidinner boom section in coaxial alignment with the piston rod of said onecylinder engageable therewith adjacent the extremity of retraction ofsaid inner boom section to define the limit of retractive movementthereof, and means including means fixed on said inner boom sectionadjacent the rear end thereof for cooperatively engaging the rearwardlyprojecting piston rod of said other cylinder adjacent the extremity ofextension of the inner boom section to define the limit of extension ofthe inner boom section.

2. A skimming mechanism according to claim 1, wherein said meanscomprises a lug fixed adjacent the rear end of said inner boom sectionand a Z-bar slidably mounted in a slot in the side walls of the outerboom section, the inner end of said Z-bar being engaged by the said lugand the outer end engageable with the rearwardly projecting end of thepiston rod of the other of said cylinders adjacent the outer extremityof travel of the inner boom section, and wherein means is provided forbiasing said Z-bar toward the rear extremity of the slot in the wall ofthe outer boomsection.

& Q

UNITED STATES PATENT OFFICE CE'HHCATE OF CGRECHUN PATENT NO. 3,913,756

DATED October 21, 1975 INVENTOR(S) i GEORGE E, BARRON and HARRY PAVONEIt is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 3, line 67, after "3,659,833" delete -No.-.

Column 9, line 47, "skimming should read -slanting- Signed and mled thistwenty-third 0? March 1976 [SEAL] A ttest:

RUTH. C. MASON C. MARSHALL DANN A IFS HIX Offi Commissioner of'larenixand Trademarks

1. In a skimming mechanism having a supporting structure, a boomassembly movably mounted on said structure, said boom assembly havingtelescoping outer and inner boom sections, anti-friction means guidablysupporting said inner boom section for reciprocative movement withinsaid outer boom section, a skimming paddle carried on the forward end ofsaid inner boom section, and power drive means for effectingreciprocative movement of said inner boom section within said outer boomsection, the improvement comprising a pair of cushioning cylinders fixedexternally at the front end of said outer boom section, one of saidcylinders having a forwardly projecting piston rod and the other of saidcylinders having a rearwardly projecting piston rod, rod means on saidinner boom section in coaxial alignment with the piston rod of said onecylinder engageable therewith adjacent the extremity of retraction ofsaid inner boom section to define the limit of retractive movementthereof, and means including means fixed on said inner boom sectionadjacent the rear end thereof for cooperatively engaging the rearwardlyprojecting piston rod of said other cylinder adjacent the extremity ofextension of the inner boom section to define the limit of extension ofthe inner boom section.
 2. A skimming mechanism according to claim 1,wherein said means comprises a lug fixed adjacent the rear end of saidinner boom section and a Z-bar slidably mounted in a slot in the sidewalls of the outer boom section, the inner end of said Z-bar beingengaged by the said lug and the outer end engageable with the rearwardlyprojecting end of the piston rod of the other of said cylinders adjacentthe outer extremity of travel of the inner boom section, and whereinmeans is provided for biasing said Z-bar toward the rear extremity ofthe slot in the wall of the outer boom section.